The present invention relates to an optic device on which an optical chip used in optical pickup systems for CDs, DVDs, MDs, and cameras such as video camera, digital cameras, and digital still cameras is mounted.
Recently, optic devices incorporated in optical pickup systems for CDs, DVDs, MDs, and cameras such as video cameras, digital cameras, and digital still cameras are provided as package units in such a fashion that the principal face of the optic device is covered with a transparent plate with an optical chip mounted on a base of the optic device made of an insulating material.
FIG. 5 is a section showing a construction of a solid-state imaging device as one example of conventional optic devices (see Japanese Patent Application Laid Open Publication No. 2002-43554A). As shown in the drawing, the solid-state imaging device includes, as main members: a frame-like base 131 made of a thermosetting resin through the central part of which an aperture 132 is formed; a solid-state imaging element 135 composed of a CCD or the like mounted on the lower face of the base 131; a transparent plate 136 made of a glass and mounted on the upper face of the base 131 so as to face the solid-state imaging element 135 through the aperture 132; and an adhesive layer 140 for mechanically connecting the transparent plate 136 to the base 131.
On the lower face of the base 131, also, a wiring 134 composed of a gold-plated layer buried in the resin of the base 131 is provided. The solid-state imaging element 135 is mounted below the base 131 so that a light receiving region 135a of the solid-state imaging element 135 is exposed to the aperture 132.
In the solid-state imaging element 135, an electrode pad (not shown) is provided for transmitting and receiving a signal between the solid-state imaging element 135 and external equipment. An internal terminal portion of the wiring 134 is exposed at the end part thereof to the aperture 132, and the internal terminal portion of the wiring 134 and the electrode pad of the solid-state imaging element 135 are electrically connected with each other through a bump (protruding electrode) 138 interposed therebetween. Further, a solder ball 141 is attached to an external terminal portion of the wiring 134. The solid-state imaging element 135, the wiring 134, and the bump 138 are sealed by a sealing resin 137 provided around the solid-state imaging element 135 on the lower face of the base 131.
The thus constructed solid-state imaging device is mounted on a circuit substrate with the transparent plate 136 facing upward as shown in the drawing. A cylinder mirror in which an imaging optical system is incorporated is fitted on the base 131, as indicated by broken lines in the drawing.
As described above, the light receiving region 135a of the solid-state imaging element 135 is arranged in the aperture 132 when viewed in plan. Light from an object to be shot is collected in the light receiving region 135a of the solid-state imaging element 135 through the imaging optical system incorporated in the cylinder mirror, and is photoelectrically converted by the solid-state imaging element 135.
Another solid-state imaging device is known in which a concave portion is formed in a part of a base where a solid-state imaging element is mounted, different from the shape of the base 131 shown in FIG. 5 (see, for example, Japanese Patent Application Laid Open. Publication No. 2000-58805A).
Recently, optic devices in which a light receiving element and a light emitting element are provided are reduced to practice. In this case, a hologram is mounted on the base 131 rather than the transparent plate 136 (hologram unit).
Wherein, in the case where both the light receiving element and the light emitting element are arranged in the optic device, it is general to mount a comparatively small light emitting element on a light receiving element.
In the conventional solid-state imaging device shown in FIG. 5, however, extremely high accuracy is required in the positional relationship between a lens system incorporated in the cylinder mirror and the optic device, and therefore, optical axes must be adjusted under conditions that the cylinder mirror is mounted to the optical device. The adjustment of the optical axes necessitates cumbersome labor.
The devices in which a hologram is mounted on the base 131 rather than the transparent plate 136 involve the same problems.